Method and arrangement for efficiently utilizing radio resources in a communication network

ABSTRACT

The present invention relates to a method and an arrangement for obtaining efficient radio resource utilization over a radio interface in a communication network comprising a transmitting entity ( 18 ) transmitting data over said radio interface to a receiving entity ( 15 ), said transmitting entity ( 18 ) comprising at least an upper layer utilizing an automatic repeat request (ARQ) protocol on top of a lower layer utilizing a hybrid automatic repeat request (HARQ) protocol, whereby a timer in said upper layer is arranged to supervise operation of said upper layer. Said timer is set based on an indication of receipt status of the transmitted data in said receiving entity ( 15 ) according to said lower layer hybrid automatic repeat request protocol.

TECHNICAL FIELD

The present invention relates to a method and an arrangement in acommunication network, and in particular to an arrangement allowing forefficiently utilizing radio resources over a radio interface as well asa method for such utilization. The invention also relates to a userequipment for efficiently utilizing radio resources over a radiointerface. The invention further relates to a computer-readable mediumcontaining computer program for efficiently utilizing radio resourcesover a radio interface.

BACKGROUND OF THE INVENTION

Protocol timers are often used, e.g., in re-transmission protocols, sothat a new message or action is repeated in case a desired outcome hasnot taken place before the timer has expired. This is the case, forexample, in the Radio Link Control (RLC) protocol in the UMTSTerrestrial Radio Access Network (UTRAN), where various timers such as,e.g., the Poll Timer is defined. The purpose of this timer is tore-transmit a Poll after the expiry of the timer to cover the situationif the Poll (or the peer's Status report) has been lost over anerror-prone link. Note that similar timers are used in almost allprotocols striving for reliability, including signaling (layer 3)protocols.

The Enhanced Dedicated Channel (E-DCH) is an uplink transport channeldefined in the Third Generation Partnership Project (3GPP) Rel 6. Onenew feature of E-DCH is the introduction of Hybrid Automatic RepeatRequest (HARQ). HARQ is also used in High Speed Downlink Shared Channel(HS-DSCH), and it is planned for the Long Term Evolution (LTE) of UTRAN.

In the E-DCH protocol stack, shown in FIG. 2, there are then two layersof retransmissions. The first retransmitting entity is the HARQ protocolon the Medium Access Control (MAC) layer, which performs retransmissionsbased on a one bit acknowledgement/negative acknowledgement (ACK/NACK).If HARQ fails, or a NACK to ACK error occurs, out-of-sequence deliveryis performed to the next retransmitting entity, which is the RLCautomatic repeat request (ARQ) protocol. RLC then cares for the residualerrors.

RLC is present at both ends of the connection; in the user equipment(UE) and in the radio network controller (RNC). Retransmissions are madebased on STATUS reports, which on the other hand are performed based ontimers and polling. In other words, RLC retransmissions can becontrolled with RLC parameters including timer values and polling rules.

RLC was already present in the previous 3GPP releases, where no HARQprotocol was used, i.e. with Dedicated Control Channel (DCH) and ForwardAccess Channel/Random Access Channel (FACH/RACH). Most RLC timer valuesare therefore typically based on an estimate of the Round-Trip-Time(RTT) on the RLC layer. With HARQ in place, however, the calculation ofRTT on the RLC layer becomes tricky. This is because the delay may varysubstantially due to the HARQ, since a payload unit in a HARQ processcan be subject to varying number of re-transmissions. The presentspecifications consider that the RTT can vary (mainly for RACH) but donot include suitable inter-layer communication for supporting thevarying HARQ delay for E-DCH.

With HARQ in operation, a correct setting of the timers in upper-layerprotocols is far from trivial. This is exemplified with an E-DCH having10 ms Transmission Time Interval (TTI) with four HARQ processes. Supposethe number of HARQ re-transmissions vary between 1 and 8. Depending onthe HARQ operation, the transmission delay can then vary between 10 msand [7×40+10] ms=290 ms.

The RLC specification (TS 25.322) defines the start of many of itstimers as follows:

-   -   “In the UE this timer shall be started (or restarted) when the        successful or unsuccessful transmission of an AMD PDU containing        a poll is indicated by lower layer”

Indeed, the MAC layer is specified to send an indication to RLC, whenthe RLC Protocol Data Units (PDU) has been submitted for transmission bythe physical layer:

-   -   MAC-STATUS-Ind/Resp:    -   [ . . . ] At the UE, MAC-STATUS-Ind primitive is also used to        indicate from MAC to RLC that MAC has requested data        transmission by PHY (i.e. PHY-DATA-REQ has been submitted), or        that transmission of an RLC PDU on RACH has failed due to        exceeded preamble ramping cycle counter.

And further (the parameter indicating the status of the transmission):

-   -   TX status:        -   when set to value “transmission unsuccessful” this parameter            indicates to RLC that transmission of an RLC PDU failed in            the previous TTI, when set to value “transmission            successful” this parameter indicates to RLC that the            requested RLC PDU(s) has been submitted for transmission by            the physical layer.

Thus, MAC is obligated to inform the RLC when the transmission of a PDUhas commenced by the physical layer. However, there is no indication ofthe successful/unsuccessful reception of the PDU at the peer entity. Inparticular, there is no definition of how to use the indication when theRLC PDUs are carried over E-DCH with HARQ. Thus, the MAC specificationis unclear in this respect.

As observed through the example above, the delay from the data requestuntil a successful transmission with HARQ has been performed can varysignificantly. Thus, in order to deal with this delay-variation, thereis a need to update the specification such that the HARQdelay-variations can be catered for by the upper layers—particularly byRLC timers.

SUMMARY OF THE INVENTION

Accordingly, it is an objective with the present invention to provide animproved method for obtaining efficient radio resource utilization overa radio interface in a communication network comprising a transmittingentity transmitting packet data over said radio interface to a receivingentity, said transmitting entity comprising at least an upper layerutilizing an automatic repeat request protocol on top of a lower layerutilizing a hybrid automatic repeat request protocol, whereby at leastone timer in said upper layer is arranged to supervise operation of saidupper layer.

Another objective with the present invention is to provide an improvedarrangement for obtaining efficient radio resource utilization over aradio interface in a communication network comprising a transmittingentity transmitting packet data over said radio interface to a receivingentity, said transmitting entity comprising at least an upper layerutilizing an automatic repeat request protocol on top of a lower layerutilizing a hybrid automatic repeat request protocol, whereby at leastone timer in said upper layer is arranged to supervise operation of saidupper layer.

A further objective with the present invention is to provide an improveduser equipment for obtaining efficient radio resource utilization over aradio interface, comprising at least an upper layer utilizing anautomatic repeat request protocol on top of a lower layer utilizing ahybrid automatic repeat request protocol, whereby at least one timer insaid upper layer is arranged to supervise operation of said upper layer.

A still further objective with the present invention is to provide animproved computer-readable medium for obtaining efficient radio resourceutilization over a radio interface in a communication network comprisinga transmitting entity transmitting packet data over said radio interfaceto a receiving entity, said transmitting entity comprising at least anupper layer utilizing an automatic repeat request protocol on top of alower layer utilizing a hybrid automatic repeat request protocol,whereby a timer in said upper layer is arranged to supervise operationof said upper layer.

Thanks to the provision of a method and an arrangement using anindication from a lower layer to make the operation of the upper layermore efficient, the amount of unneeded waiting times is reduced. And, bymaking the timer values more accurate, a more efficient transfer on theupper layer is obtained, minimizing problems of window stalling andunnecessary retransmissions. Thus, the radio resources are moreefficiently utilized.

Still other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 shows the communication network architecture according to thepresent invention;

FIG. 2 shows the protocol termination for E-DCH, user plane;

FIG. 3 is an information flow according to a first embodiment of thepresent invention;

FIG. 4 is an information flow according to a second embodiment of thepresent invention;

FIG. 5 is an information flow according to a fifth embodiment of thepresent invention;

FIG. 6 shows a computer-readable medium.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 depicts a communication system, such as a Wideband Code DivisionMultiple Access (WCDMA) communication system, including a Radio AccessNetwork (RAN), such as the UMTS Terrestrial Radio Access Network (UTRAN)architecture, comprising at least one Radio Base Station (RBS) (or NodeB) 15 connected to one or more Radio Network Controllers (RNCs) 10. TheRAN is connected to a Core network (CN) 12. The RAN and the CN 12provide communication and control for a plurality of user equipments(UE) 18 (only one is shown in FIG. 1), that each uses downlink (DL)channels 13 and uplink (UL) channels 14 for transmitting and receivingdata/signals. According to a preferred embodiment of the presentinvention, the communication system is herein described as a WCDMAcommunication system. The skilled person, however, realizes that theinventive method and arrangement works very well on other communicationssystems as well.

The key finding for the present invention is the fact that HARQfacilitates knowledge about when a PDU actually has been successfullyreceived at the receiving peer-entity. Thus, the upper-layer protocoltimers can be started based on the HARQ feedback.

Without the present idea, and using timer-values that account for theworst-case, HARQ delay may decrease the performance, because long timersmight prevent window gliding and re-transmissions of lost data andsignalling messages.

Below the invention is described by using primitives (or signals) thatare exchanged between the different protocol entities in a similar wayas is done in the 3GPP specifications. This is just a descriptive methodand should not restrict the invention in any way. Further, according toa preferred embodiment of the present invention, the protocols usedherein, i.e. RLC and MAC, are only examples taken from the current 3GPPspecifications. The person skilled in the art realizes that theinvention works well on other protocols as well.

As mentioned above the timers in RLC are usually set based on the RTTbetween the protocol entities. Different timers in RLC have differentfunctionality such as supervision of peer entity response, prohibitingexcessive transmissions of certain peer-to-peer signaling etc. This isnot discussed further here.

Currently as described in 3GPP, relevant timers are started/re-started,when the PHY-DATA-REQ primitive has been sent from MAC and MAC hasindicated this to the RLC with a MAC-STATUS-IND primitive in theparameter “TX Status”.

According to the preferred embodiment of the present invention, theMAC-STATUS-IND provides a new parameter indicating the HARQ feedbackstatus. The indication also includes a field indicating the number ofHARQ attempts used. The triggering and content of the indication isbased on the success or failure of the HARQ transmission, which ismonitored by observing the ACK/NACK feedback response from the peer HARQentity. This may also include the absence of the ACK/NACK feedback whichthen could be interpreted as a NACK. Reception of an ACK triggers anindication to RLC including information of successful delivery of thePDU. Similarly, the reception of a NACK could trigger an indication toRLC including information of unsuccessful delivery either every time aNACK is received or when the final re-transmission also failed.Alternatively, the triggering of the indication can be performed eachtime the number of HARQ re-transmissions exceeds a pre-defined number ofattempts. Further, if MAC detects that the maximum number of HARQtransmissions has been exceeded without any ACK this can be indicated toRLC.

The upper-layer reaction to the proposed indications includes differentpossible embodiments: The main embodiment is to start and/or restartrelevant timers based on the indication of successful or unsuccessfulreception of the PDU by the peer HARQ entity. Another embodiment is tore-transmit the PDUs in case the aforementioned indication indicates afailure in the HARQ delivery.

According to the present invention a method is provided for obtainingefficient radio resource utilization over a radio interface in acommunication network comprising a transmitting entity, such as a UE,transmitting data/signals over said radio interface to a receivingentity, such as the RNC or Node B, said entities comprising at least anupper layer, e.g. an RLC layer, utilizing an automatic repeat request(ARQ) protocol on top of a lower layer, e.g. a MAC layer, utilizing ahybrid automatic repeat request (HARQ) protocol, whereby at least onetimer in said upper layer is arranged to supervise operation of saidupper layer. The method comprises the step of setting said at least onetimer based on an indication, e.g. an ACK/NACK message of receipt statusof the transmitted data/signals in said receiving entity according tosaid lower layer HARQ protocol.

Also, according to the present invention a user equipment 18 is providedfor obtaining efficient radio resource utilization over a radiointerface, comprising at least an upper layer utilizing an automaticrepeat request protocol on top of a lower layer utilizing a hybridautomatic repeat request protocol, whereby at least one timer in saidupper layer is arranged to supervise operation of said upper layer. Theuser equipment comprises means for setting said at least one timer basedon feedback of receipt status of the transmitted data in a receivingentity, such as the RNC or Node B, according to said lower layer hybridautomatic repeat request protocol.

FIG. 3 shows a flow chart according to a first preferred embodiment ofthe present invention, wherein the relevant RLC timers arestarted/re-started at the reception of feedback for asuccessful/unsuccessful delivery. When the RLC PDU is submitted to thephysical layer for transmission, wait until an ACK (or HARQ failure) forthat particular PDU(s) has been received. Thus, a MAC-DATA-Req 31 issent from the RLC to the MAC and a PHY-DATA Req 32 is sent from the MACto the Physical layer (PHY). A first HARQ transmission 33 is sent fromthe transmitter (the UE) to the receiver (the RBS). If the transmissionis successfully received, the receiver sends an ACK 36 back to thetransmitter. However, as long as the transmission is unsuccessfullyreceived, the receiver sends a NACK 34 back to the transmitter, wherebythe transmitter re-transmits the HARQ transmission 35 up to apre-determined maximum number of re-transmissions. If no successfultransmissions have been made after the maximum number ofre-transmission, the transmission is seen as a HARQ failure. Afterhaving received an ACK of a HARQ failure at 36, the PHY sends aPHY-STATUS-Ind 37 to the MAC, whereby the MAC sends a MAC-STATUS-Ind 38to the RLC.

FIG. 4 shows a flow chart according to a second preferred embodiment ofthe present invention, wherein the relevant RLC timers are started atthe reception of feedback for the x:th HARQ transmission. When the PDUis submitted to the physical layer for transmission, wait until it hasbeen sent and ACKed or sent for the x:th time and NACked, and thennotify the upper layers about the transmission status of the PDU. Thissolution enables slightly lower timer values, but does not fully utilizethe HARQ information available. Thus, a MAC-DATA-Req 41 is sent from theRLC to the MAC and a PHY-DATA Req 42 is sent from the MAC to thePhysical layer (PHY). A first HARQ transmission 43 is sent from thetransmitter (the UE 18) to the receiver (the RBS 15). If thetransmission is successfully received, the receiver sends an ACK back tothe transmitter. However, as long as the transmission is unsuccessfullyreceived, the receiver sends a NACK 44 back to the transmitter, wherebythe transmitter re-transmits the HARQ transmission. If the transmissionat a pre-determined number of re-transmissions 45, i.e. not the maximumnumber, still not is successfully received and being NACK:ed 46, the PHYsends a PHY-STATUS-Ind 37 to the MAC, whereby the MAC sends aMAC-STATUS-Ind 38 to the RLC.

According to a third preferred embodiment or the present invention (notshown), a direct re-transmission of the lost upper-layer PDU isperformed based on the reception of a HARQ failure indication.

According to a fourth preferred embodiment of the present invention (notshown), the interaction between MAC-HARQ and RLC may also be deployed onthe receiver side. The MAC-HARQ layer may in some conditions discoverthat an error in the HARQ feedback signalling has occurred. An exampleof this is when HARQ has requested a retransmission of a MAC PDU bysending a HARQ NACK but a new MAC PDU is received instead of theretransmission. This event is an indication of that a data loss hasoccurred on HARQ level and the event could be indicated to the RLClayer. The RLC layer may, when this indication is received, immediatelytransmit an RLC STATUS report to make the peer RLC entity aware of thedata loss, even if the status prohibit timer is running. Alternatively,the RLC entity should only send the STATUS report if the status prohibittimer is not running when the indication from MAC is received.

FIG. 5 shows a flow chart according to a fifth preferred embodiment ofthe present invention, wherein the HARQ feedback information is sentfrom MAC to RLC for every transmission attempt in the HARQ entity. Thetimers in RLC are started at the first transmission attempt and thenre-started as a result of the HARQ feedback response (ACK/NACK). Itshould be noted that the prohibiting function is started already beforethe timer, namely when the prohibit function is triggered. FIG. 5 showsthe flow between the UE 18 and the RBS 15 (or Node B). The RLC layer ofthe UE 18 sends a MAC-DATA-REQ 51 to the MAC layer of the UE 18. The MAClayer sends a PHY-DATA-REQ 52 to the PHY layer of the UE 18 and aMAC-STATUS-IND 53 back to the RLC whereby the timers of the RLC layerare started. The PHY layer of the UE 18 sends a first HARQ transmission54 to the PHY layer of the RBS 15, which sends a PHY-DATA-IND 55 to theMAC layer of the RBS 15. If the transmission is unsuccessfully received,the MAC layer of the RBS 15 sends a NACK 56 to the MAC layer of the UE18, and the MAC of the UE 18 sends a MAC-STATUS-IND 53 to the RLC,whereby the timers are re-started. The procedure is repeated, i.e. theMAC of the UE 18 sends a PHY-DATA-REQ 52 to the PHY layer of the UE 18and so forth. In the example of FIG. 5, the third transmission attemptis successfully received, whereby the MAC of the RBS 15 sends an ACK 57back to the MAC of the UE 18.

Alternatively, according to a sixth preferred embodiment of the presentinvention (not shown), the RLC is changed to start a long timer, whichis at least as long as the max transmission delay counting all HARQtransmission attempts, when the PDU is submitted for transmission. Thetimer is then re-started/updated with the correct timer value that is inthe order of the RTT value according to the first preferred embodiment,i.e. when either an ACK or max number of re-transmissions is reached.

It will be appreciated that at least some of the procedures describedabove are carried out repetitively as necessary to respond to thetime-varying characteristics of the channel between the transmitter andthe receiver. To facilitate understanding, many aspects of the inventionare described in terms of sequences of actions to be performed by, forexample, elements of a programmable computer system. It will berecognized that the various actions could be performed by specializedcircuits (e.g. discrete logic gates interconnected to perform aspecialized function or application-specific integrated circuits), byprogram instructions executed by one or more processors, or acombination of both.

Moreover, the invention can additionally be considered to be embodiedentirely within any form of computer-readable storage medium, exemplaryshown in FIG. 6 and denoted with 60, having stored therein anappropriate set of instructions for use by or in connection with aninstruction-execution system, apparatus or device, such ascomputer-based system, processor-containing system, or other system thatcan fetch instructions from a medium and execute the instructions. Asused here, a “computer-readable medium” can be any means that cancontain, store, communicate, propagate, or transport the program for useby or in connection with the instruction-execution system, apparatus ordevice. The computer-readable medium can be, for example but not limitedto, an electronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, device or propagation medium. Morespecific examples (a non-exhaustive list) of the computer-readablemedium include an electrical connection having one or more wires, aportable computer diskette, a random access memory (RAM), a read onlymemory (ROM), an erasable programmable read only memory (EPROM or Flashmemory), an optical fibre, and a portable compact disc read only memory(CD-ROM).

Thus, a computer-readable medium containing computer program accordingto a preferred embodiment of the present invention for obtainingefficient radio resource utilization over a radio interface in acommunication network comprising a transmitting entity transmittingpacket data over said radio interface to a receiving entity, saidentities comprising at least an upper layer utilizing an automaticrepeat request protocol on top of a lower layer utilizing a hybridautomatic repeat request protocol, whereby at least one timer in saidupper layer is arranged to supervise operation of said upper layer, isprovided wherein the computer program performs the step of setting saidat least one timer based on an indication of receipt status of thetransmitted packet data in said receiving entity according to said lowerlayer hybrid automatic repeat request protocol.

The invention may be embodied in many different forms, not all of whichare described above, and all such forms are contemplated to be withinthe scope of the invention. For each of the various aspects of theinvention, any such form may be referred to as “logic configured to”perform a described action, or alternatively as “logic that” performs adescribed action.

Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

Expressions such as “including”, “comprising”, “containing”,“incorporating”, “consisting or”, “have”, “is” used to describe andclaim the present invention are intended to be construed in anon-exclusive manner, namely allowing for items, components or elementsnot explicitly described also to be present. Reference to the singularis also to be construed to relate to the plural and vice versa.

Numerals included within parentheses in the accompanying claims areintended to assist understanding of the claims and should not beconstrued in any way to limit subject matter claimed by these claims.

The invention claimed is:
 1. A method in a transmitting entity forobtaining efficient radio resource utilization over a radio interface ina communication network comprising said transmitting entity transmittingdata over said radio interface to a receiving entity, said transmittingentity comprising at least an upper layer utilizing an automatic repeatrequest protocol on top of a lower layer utilizing a hybrid automaticrepeat request protocol, the method comprising: setting at least onetimer based on an indication of receipt status of the transmitted datain said receiving entity according to said lower layer hybrid automaticrepeat request protocol, wherein setting the at least one timercomprises setting the at least one timer based on the indication ofreceipt status being received at the upper layer from the lower layer;and supervising operation of the upper layer using the at least onetimer; wherein said indication of receipt status of the transmitted datais sent from said lower layer to said upper layer for every transmissionattempt of the transmitted data from the lower layer over the radiointerface, wherein said at least one timer is started at the firsttransmission attempt of the transmitted data and re-started when saidindication of receipt status of the transmitted data is received.
 2. Amethod according to claim 1, where said indication of receipt status ofthe transmitted data indicates successful transmission of thetransmitted data in said lower layer.
 3. A method according to claim 1,where said indication of receipt status of the transmitted dataindicates unsuccessful transmission of the transmitted data in saidlower layer.
 4. A method according to claim 3, where said indication ofunsuccessful transmission of the transmitted data is sent from saidlower layer to said upper layer after a pre-determined number ofunsuccessful transmission attempts of the transmitted data has beenmade.
 5. A method according to claim 1, where said indication of receiptstatus of the transmitted data is sent from said lower layer to saidupper layer when a loss of the transmitted data has occurred.
 6. Amethod according to claim 5, where the method further comprises:directly re-transmitting said lost data to said receiving entity whensaid indication of receipt status of the transmitted data is received insaid upper layer.
 7. A method according to claim 1, where saidindication of receipt status of the transmitted data indicates asignaling error in said lower layer, and where a message of saidsignaling error is sent from said upper layer to a second receivingentity.
 8. A method according to claim 1, where said at least one timeris set to last until a maximum number of transmission attempts of thetransmitted data is reached.
 9. A method according to claim 1, wheresaid upper layer is a radio link control (RLC) layer and said lowerlayer is a medium access control (MAC) layer.
 10. A method according toclaim 1 wherein said at least one timer is started at the firsttransmission attempt of the transmitted data, wherein said at least onetimer is re-started responsive to receiving a negative acknowledgmentreceipt status of the transmitted data, and wherein said at least onetimer is re-started responsive to receiving a acknowledgment receiptstatus of the transmitted data.
 11. An arrangement in a transmittingentity for obtaining efficient radio resource utilization over a radiointerface in a communication network comprising said transmitting entitytransmitting data over said radio interface to a receiving entity, saidtransmitting entity comprising at least an upper layer utilizing anautomatic repeat request protocol on top of a lower layer utilizing ahybrid automatic repeat request protocol, the arrangement comprises:means for setting at least one timer based on an indication of receiptstatus of the transmitted data in said receiving entity according tosaid lower layer hybrid automatic repeat request protocol, wherein themeans for setting the at least one timer comprises means for setting theat least one timer based on the indication of receipt status beingreceived at the upper layer from the lower layer; and means forsupervising the upper layer using the at least one timer; wherein saidlower layer is arranged to send said indication of receipt status of thetransmitted data to said upper layer for every transmission attempt ofthe transmitted data from the lower layer over the radio interface,wherein said at least one timer is started at the first transmissionattempt of the transmitted data and restarted when said indication ofreceipt status of the transmitted data is received.
 12. An arrangementaccording to claim 11, where said indication of receipt status of thetransmitted data indicates successful transmission of the transmitteddata in said lower layer.
 13. An arrangement according to claim 11,where said indication of receipt status of the transmitted dataindicates unsuccessful transmission of the transmitted data in saidlower layer.
 14. An arrangement according to claim 13, where said lowerlayer is arranged to send said indication of unsuccessful transmissionof the transmitted data to said upper layer after a pre-determinednumber of unsuccessful transmission attempts of the transmitted data hasbeen made.
 15. An arrangement according to claim 11, where said lowerlayer is arranged to send said indication of receipt status of thetransmitted data to said upper layer when a loss of the transmitted datahas occurred.
 16. An arrangement according to claim 15, where saidtransmitting entity is arranged to directly re-transmit said lost datato said receiving entity when said indication of receipt status of thetransmitted data is received in said upper layer.
 17. An arrangementaccording to claim 11, where said indication of receipt status of thetransmitted data indicates a signaling error in said lower layer, wheresaid upper layer is arranged to send a message of said signaling errorto a second receiving entity.
 18. An arrangement according to claim 11,where said means for setting said at least one timer is arranged to setsaid at least one timer to last until a maximum number of transmissionattempts of the transmitted data is reached.
 19. An arrangementaccording to claim 11, where said upper layer is a radio link control(RLC) layer and said lower layer is a medium access control (MAC) layer.20. An arrangement according to claim 11 wherein said at least one timeris started at the first transmission attempt of the transmitted data,wherein said at least one timer is re-started responsive to receiving anegative acknowledgment receipt status of the transmitted data, andwherein said at least one timer is re-started responsive to receiving aacknowledgment receipt status of the transmitted data.